The filling of small tanks with liquids has long been a source of inventive ideas, particularly as small gasoline motors and kerosene heaters have proliferated. The environmental damage from spillage during filling has caused the Environmental Protection Agency to include spillage as a significant pollution source. One early variation was developed to fill batteries with acid, which used a float to indicate full condition (U.S. Pat. No. 721,870 to T. A. Edison). Inventions of many other types have resulted as numerous inventors have endeavored to more satisfactorily solve this spillage problem.
Funnels have been designed with almost every type of signal to indicate when the tank is full. Some devices require the small vessel containing the source liquid to be equipped with special spouts. Some spouts have a mechanical trip valve at the end which rests on the mouth of the tank to be filled, with the operator moving the source liquid tank to open or close the trip valve, making such decision by observing the liquid level through the tank opening. A common problem with the valved spouts is visually seeing the liquid level inside the tank so as to know when to stop pouring. Frequently, the first indication of being "filled" is also an overflow.
Some have spouts which contain two passages, one for liquid being poured, the other for the return air, and the dual passage spout is inserted into the to-be-filled tank's opening. When the liquid level therein rises with filling, the return air vent is covered so that flow characteristics change, and the operator then lowers the source tank to where flow isn't possible.
In a variation of the return air control, a dual passage, transparent connection line is connected to the openings of both the tank to be filled and the source tank. The operator observes the return flow through the transparent connection line and controls the flow by raising or lowering the source tank.
Each of these inventions has had some shortcoming, as none has become a universally accepted solution. A general problem with prior funnel devices has been either their complexity (valves, air passages, etc.) or the funnel's resting in the tank opening which obscures the view of the liquid level in the tank or simply the correct size device is not convenient to the operator when filling occurs, or a combination of these causes.
Funnels are desirable so as to provide an enlarged entrance and are particularly desirable when pouring takes place in a hurry.
However, in general, there are two other common problems with funnels: seeing the liquid level as the tank becomes full and what to do with the "lag time" liquid that invariably occurs between seeing that "full" is about to occur and lowering or adjusting the source tank so as to actually cause flow to stop. The "lag time" liquid can represent a substantial amount and is particularly dangerous if it is spilled due to overfilling. In addition, it is desirable to not solidly connect the to-be-filled tank to the source tank, both because of the physical constraints and because of potential leak sources created during filling.
Accordingly, it is desirable to have a funnel to introduce the filling liquid into the mouth of the to-be-filled tank, allowing free-flow from the source tank (or its nozzle). It is also desirable to provide an easily visible early level indication that a "full" condition is about to be reached. It is further desirable that the funnel exits be sized and shaped so that the only time liquid accumulates in its lower portion is when the tank below cannot accept further liquid, i.e., is full. Accordingly, the funnel preferably accepts various flow rates without backup. It is even further desirable to provide a method of accepting a "lag time" apparent overfill without a resultant spill no matter what specific type of spout is used. It is still further desirable that such overfill method control be independent of the orientation or shape of the tank to be filled (i.e., if an air gap is created in the tank by the location of the return air vent in a sealably engaged funnel device, the air gap can easily vary in volume depending on the shape and/or orientation of the tank at the time it is being filled).
Yet another frequently desirable feature is to have the filling unit carried with and as part of the tank to be filled, but in a manner so as to not interfere with nearby functions, and all in a manner that is so simple and foolproof to use that operators welcome its provision. U.S. Pat. No. 4,256,154 discloses a retractable funnel; however, the problem of overfill is not solved by providing a funnel alone.